Sunday, 6 September 2015

How to prevent warping of MDF boards and bases

I expect we've all seen it ... a lovely terrain piece that is slightly spoiled by the base having warped after the texture, paint, grass, etc has been applied. I have a couple of such items in my collection. So I set about experimenting with ways to prevent it. This is what I've learned ...

The base for the field (from my previous post) ready to be pre-curved. Ideally I would not apply any texture first in case it fell off when the board is being curved, but in my enthusiasm to get it done, I forgot. Doh!? Approx size 26cm x 21cm, of 3mm MDF.

Prop it carefully, upside-down, between two books. The edges just need to reach the books. I've found that for rectangular boards you should pre-curve along the longest dimension.

Place a small, solid item in the middle of the board – it just helps to focus the force of the weight that goes on top.

Now stack PLENTY of heavy books on top. MDF will take quite a bit of weight! This must have been in excess of 5Kg's.

This board is 26cm wide and is bent by approx, 1cm.

Leave for at least 24 hours, preferrably 48 hours. Then remove the books and do whatever you’re planning to do with the board right away, e.g. sand, paint, etc. After removing the books and turning the board back the right way up it should still have a slightly raised arch. The 'pre-curving' should offset the warping effect of paint/glue. Occasionally the board stays slightly ‘arched’ but they seem to flatten after a while.

Make sure the finished items are stored flat otherwise they can be prone to warping even after some time.

It's not an exact science but it does seem to work quite well compared to other techniques such as scoring or painting the opposite side.

Hope that's useful.


Rodger said...

Interesting! I might give this idea a try sometime. Thanks Matt.

Robbie Rodiss said...

Afternoon Matt,
Re the MDF warping. I have made loads of wargames terrain over the years based on 2 foot square mdf boards. The way to stop them warping is really quite simple after I was shown by a painter and decorator! Buy some cold water wall paper paste, mix as per the instructions, brush both sides of the board all over, covering the whole board. It does get messy, so go outside.Allow to dry thoroughly and then work your magic. Honest it really works. Give it a try on a test board. Some of my boards are over 30 years old, and only a couple have warped, and that was down to storing them in my garage for a year.

Gary said...

Great tip on fixing a warp broad.

mehrunes said...

My eyperience is that you simply have to apply the same forces in the other side. So when you apply white glue to the top to fix same or something, just apply roughly the same amount of glue under the finished piece and for example fix a sheet of paper to the bottom. This way both sides come under the same effect of the warping force of the glue, hopefully cancelling each other out.